An Acrocarpous Moss in Cretaceous Amber from Myanmar
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Cretaceous Research 51 (2014) 260e265 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes An acrocarpous moss in Cretaceous amber from Myanmar * Jochen Heinrichs a, , Alfons Schafer-Verwimp€ b, Lars Hedenas€ c, Michael S. Ignatov d, Alexander R. Schmidt e a Systematische Botanik und Mykologie, Department für Biologie I, Ludwig-Maximilians-Universitat,€ Menzinger Str. 67, 80638 München, Germany b Mittlere Letten 11, 88634 Herdwangen-Schonach,€ Germany c Department of Botany, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden d Main Botanical Garden, Russian Academy of Sciences, Botanicheskaya 4, Moscow 127276, Russia e Courant Research Centre Geobiology, Georg-August-Universitat€ Gottingen,€ Goldschmidtstraße 3, 37077 Gottingen,€ Germany article info abstract Article history: Recent studies have indicated considerable changes in the lineage composition of mosses during the Received 29 May 2014 Cretaceous terrestrial revolution. However, Cretaceous moss fossils are generally rare. Here we describe a Accepted in revised form 23 June 2014 sterile gametophyte fragment of an acrocarpous moss preserved in mid-Cretaceous amber from Available online 12 July 2014 Myanmar. The fossil at hand is assigned to the extant Dicranales based on its narrowly lanceolate, awned leaves with a single costa, quadrate-rectangular, bulging leaf cells forming a serrate leaf margin, and Keywords: oblong-ovate leaf bases with hyaline, rectangular cells. The protruding cells of the awns point to the Bryopsida possibility that they previously carried gemmae, as is seen in numerous extant representatives of the Burmese amber Calymperaceae Calymperaceae genera Calymperes and Syrrhopodon. The fossil differs from both genera by its indistinctly Calymperites separated hyaline basal leaf cells, and is placed in the form genus Calymperites as C. burmensis sp. nov. Dicranales © 2014 Elsevier Ltd. All rights reserved. Fossil Taxonomy 1. Introduction Krassilov and Schuster, 1984; Ignatov, 1992; Ignatov and Shcherbackov, 2011a). The situation takes a turn for the better in With some 9000e13,000 extant species, mosses represent the the Cretaceous. Here, a few excellently preserved fossils were most speciose lineage of bryophytes (Renzaglia et al., 2007; Magill, assigned to extant families (Eopolytrichum antiquum Konopka, 2010). This lineage originated in the Paleozoic (Clarke et al., 2011; Herend., G.L. Merr. & P. Crane, Polytrichaceae; Konopka et al., 1997) Fiz-Palacios et al., 2011; Magallon et al., 2013), but the recon- or genera (Campylopodium allonense Konopka, Herend. & P. Crane, struction of its evolutionary history is hampered by its sparse fossil Dicranaceae; Konopka et al., 1998). However, documented evidence record and the incomplete preservation of most fossils (Krassilov of Cretaceous moss fossils is scarce. Cretaceous moss fossils are and Schuster, 1984; Oostendorp, 1987; Taylor et al., 2009; Kenrick urgently needed to scrutinize the hypothesis of major changes in et al., 2012). The earliest fossils which have been assigned to the lineage composition of mosses during the late Mesozoic, which mosses date back to the Carboniferous, but their taxonomic status were recently postulated based on molecular data (Shaw et al., is ambiguous (Renault and Zeiller, 1885; Lignier, 1914; Thomas, 2003; Newton et al., 2007; Fiz-Palacios et al., 2011). 1972; Hübers and Kerp, 2012). The classification of Permian, In the present paper we describe an inclusion of an acrocarpous Triassic or Jurassic mosses is likewise difficult because many moss in a piece of Cretaceous amber from Myanmar, and discuss its taxonomically relevant characters are not preserved. Moreover, the relationships to extant and extinct taxa. available morphological character states do not fully overlap with those of extant genera or families (Heinrichs et al., 2014c). 2. Materials and methods Accordingly, these fossils are usually assigned to form genera or genera with unclear taxonomic relationships (Neuburg, 1960; The amber piece was found at the famous amber locality near the village of Tanai which is located on the Ledo Road about 105 km north of Myitkyina in Kachin State, Myanmar (see Figure 1 in * Corresponding author. Grimaldi et al., 2002), and it has been transferred to the amber E-mail addresses: [email protected] (J. Heinrichs), [email protected] (L. Hedenas),€ [email protected] (M.S. Ignatov), [email protected] collection of the American Museum of Natural History in New York goettingen.de (A.R. Schmidt). (collection number AMNH Bu ASJH-2). Syninclusions of the http://dx.doi.org/10.1016/j.cretres.2014.06.010 0195-6671/© 2014 Elsevier Ltd. All rights reserved. J. Heinrichs et al. / Cretaceous Research 51 (2014) 260e265 261 unidentified bryophyte are two dipterans, a mite, a branched plant Diagnosis. hair and detritus fragments. Upright gametophytes with leaves narrowing from an oblong- Both biostratigraphic data obtained from the amber-bearing ovate base consisting of mostly elongate, hyaline cells into a sediment and the amber inclusions indicate a mid-Cretaceous age lanceolate upper region consisting of brownish cells; hyaline basal of the amber (Grimaldi et al., 2002; Cognato and Grimaldi, 2009). leaf cells not sharply separated from thick-walled upper leaf cells, Based on marine microfossils and ammonites from this amber lo- leaf margin serrate-dentate, costa extending to leaf apex, some- cality, Cruickshank and Ko (2003) suggest a late Albian age of the times forming an awn that possibly produces propagules. amber-bearing sediment, hence the inclusions have an age of Description. approximately 100 Ma, with a minimum age of 98 Ma (earliest Single sterile, unbranched gametophyte, ca. 4 mm long but Cenomanian) that is based on recent UePb dating of zircons (Shi lowermost portion not preserved; leaves crisped when dry, erect- et al., 2012). spreading when moist, ca. (1.5e)1.8e2.5 mm  0.34 mm, The amber piece was originally intended to be integrated into a sheathing with an oblong-ovate base that abruptly to gradually necklace and represents the counterpart of BU ASJH-1, which tapers into a narrowly lanceolate upper region, apex usually awned, contains an inclusion of the extinct liverwort Gackstroemia cretacea occasionally acute or narrowly truncate; margin flat or lower Heinrichs, Schaf.-Verw.,€ Feldberg, & A.R. Schmidt (Heinrichs et al., 20e40% weakly recurved, finely serrulate, near apex often with a 2014b). After an initial inspection of the inclusion, the piece of few, triangularly protruding, large, somewhat hyaline cells; costa amber was embedded in a high-grade epoxy resin [EPO-TEK 301-2, single, percurrent to excurrent, ventrally convex and obviously Epoxy Technology Inc., mixing ratio 100 (resin) : 37 (hardener)] in a built of several cell layers; upper laminal cells subquadrate to short- procedure that is based on the protocols described by Nascimbene rectangular, (6e)8e13(e15)  6e10 mm, thick-walled, opaque, and Silverstein (2000). After curing, the sample was trimmed and bulging, towards the margin apparently partially bistratose (much polished on opposite sides using a series of wet silicon carbide more opaque than other lamina cells); basal cells hyaline, (sub- abrasive papers (firm Struers, Germany) with decreasing grit sizes quadrate to) rectangular, ca. 10e40  10e22 mm, thin-walled, filling [grit from FEPA P 600e4000 (25.8 mmto5mm particle size)] to the complete leaf base, gradually turning into thick-walled upper minimize light scattering for the investigation. cells. The preparation was studied under a Carl Zeiss Stemi 2000 dissection microscope and a Carl Zeiss AxioScope A1 compound Derivation of name: Refers to the origin of the amber. microscope, each equipped with a Canon 60D digital camera. In some instances, incident and transmitted light were used simul- taneously. The images of Figs. 1 and 2 are digitally stacked photo- 3.2. Key to the species of Calymperites micrographic composites of up to 40 individual focal planes obtained using the software package HeliconFocus 5.0 for a better 1. Distal portion of leaves oblong-lingulate, costa extending to leaf illustration of the three-dimensional inclusions. apex……………C. ucrainicus 1*. Distal portion of leaves lanceolate, costa often excurrent, 3. Results forming an awn………C. burmensis 3.1. Systematic palaeontology 4. Discussion Phylum: Bryophyta Amber, fossilized tree resin, is a prime preservation agent for soft-bodied biological structures such as fungi, algae, and bryo- Class: Bryopsida phytes (Grimaldi, 1996). Fossiliferous amber is known from the Subclass: Dicranidae Triassic onwards (Schmidt et al., 2006, 2012) but bryophyte in- clusions have so far been recognized only in a few Cretaceous Order: Dicranales (s.l.) (Bell and York, 2007; Heinrichs et al., 2011) and Cenozoic deposits Family incertae sedis (but see Discussion) (e.g., Grolle and Meister, 2004; Heinrichs et al., 2014a). Several Cenozoic amber deposits are well-known for their rich inclusions Genus Calymperites Ignatov & Perkovsky, Arctoa 22 (2013): 90. of mosses. Eocene Baltic and Rovno amber, Oligocene Bitterfeld Emended diagnosis. amber, and Miocene Dominican amber yield a considerable di- Gametophytes with spirally inserted leaves narrowing from an versity of well preserved moss inclusions that allowed for detailed oblong-ovate base into a lanceolate upper region or leaves oblong- investigations not only of the gross morphology of the gameto- lingulate; upper